1. Field of the Invention
The present invention relates to a detection device that detects an object, and more particularly to a positioning mechanism of a light receiving element and an optical system.
2. Description of the Related Art
Conventionally, an object detection device, such as a focus detection device, provided to an optical device such as a camera has been constituted by a light receiving element that detects an object image, and an optical system, such as a lens, that forms the object image on the light receiving element. In such a configuration, in order to appropriately detect the object image, the light receiving element is positioned with respect to the optical system and fixed to the optical system.
Japanese Patent No. 4250235 discloses a structure in which a supporting member is provided between an optical-system holding member that holds an optical system and a light-receiving-element holding member that holds a light receiving element to position the light receiving element on multiple axes.
However, in the structure disclosed in Japanese Patent No. 4250235, the optical-system holding member and the supporting member, and the supporting member and the light-receiving-element holding member respectively abut against each other, which causes a friction therebetween at the time of positioning the light receiving element. This friction consequently results in a difference between a drive amount instructed at the time of the positioning and an actual drive amount, which makes it difficult to quickly and highly accurately position the light receiving element.
As a solution to this problem, a structure is known in which the optical-system holding member and the light-receiving-element holding member do not contact with each other. This structure in which the optical-system holding member and the light-receiving-element holding member do not contact with each other does not result in the friction, which makes it possible to quickly and highly accurately position the light receiving element.
Japanese Patent Laid-Open No. H5-210046 discloses a fill-in-adhesion structure in which the optical-system holding member and the light-receiving-element holding member do not contact with each other and in which a clearance between them is filled with adhesives to fix them.
However, in the fill-in-adhesion structure disclosed in Japanese Patent Laid-Open No. H5-210046, the positioning of the light receiving element may result in non-uniformity in distance between the optical-system holding member and the light-receiving-element holding member, that is, in length of the adhesives in a clearance direction. In the fill-in-adhesion structure, a change in surrounding hygrothermal environment inevitably causes the filled-in adhesives to expand or shrink. Because of the non-uniformity in length of the adhesives in the clearance direction, the expansion or the shrink of the adhesives causes the optical-system holding member and the light-receiving-element holding member to be acted upon by stresses with mutually different magnitudes applied from the adhesives. This causes the light receiving element to be moved, with respect to the optical system, to a position different from that corresponding to when the light receiving element is fixed with the adhesives, which makes it impossible for the light receiving element to acquire an appropriate object image. That is, the fill-in-adhesion structure disclosed in Japanese Patent Laid-Open No. H5-210046 has a problem that an accuracy in detecting the object decreases due to the change in surrounding hygrothermal environment.